Related Experiment Video
Updated: Jul 29, 2026

07:27
Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
Published on: April 29, 2010
Transcription initiation-defective forms of sigma(54) that differ in ability To function with a heteroduplex DNA
M T Kelly1, J A Ferguson, T R Hoover
1Department of Microbiology, University of Georgia, Athens, Georgia 30602, USA.
Journal of Bacteriology
|October 29, 2000
Summary
Mutant sigma(54)-RNA polymerase holoenzyme forms were studied. Some mutants initiated transcription without an activator, revealing new insights into transcription initiation regulation.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Sigma(54)-RNA polymerase holoenzyme transcription requires an activator for promoter complex isomerization.
- Activators are essential for converting closed promoter complexes to open complexes.
Purpose of the Study:
- To investigate mutant forms of Salmonella enterica serovar Typhimurium sigma(54) affecting transcription initiation.
- To identify specific sigma(54) sequences involved in regulating activator-dependent transcription.
Main Methods:
- Analysis of mutant sigma(54) proteins with defects in transcription initiation.
- Assaying activator-independent transcription using a heteroduplex DNA template.
- Characterizing mutations within conserved and non-conserved regions of sigma(54).
Main Results:
- Four mutant sigma(54) proteins exhibited activator-independent transcription.
- One mutant (L124P V148A) had substitutions in a previously uncharacterized region.
- Mutants with substitutions in the conserved Leu-179 to Leu-199 segment showed reduced activator-independent transcription.
Conclusions:
- Specific regions of sigma(54) play critical roles in preventing activator-independent transcription.
- The conserved 20-amino-acid segment (Leu-179 to Leu-199) is implicated in transcription initiation regulation.
- Understanding these mechanisms can inform studies on bacterial transcription control.
Related Concept Videos
Mismatch Repair
Overview
Translesion DNA Polymerases
Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
Bacterial Transcription
RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, transcription and translation occur simultaneously, on the same DNA template.
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are:
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are:
Transcription Initiation
Initiation is the first step of transcription in eukaryotes. Prokaryotic RNA Polymerase (RNAP) can bind to the template DNA and start transcribing. On the other hand, transcription in eukaryotes requires additional proteins, called transcription factors, to first bind to the promoter region in the DNA template. This binding helps recruit the specific RNAP that can assemble on the DNA and start transcription.
The promoters and enhancers and their accessory proteins allow tight regulation of...
The promoters and enhancers and their accessory proteins allow tight regulation of...
Mismatch Repair
Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Transcription in Prokaryotes
Transcription is a highly regulated process that converts genetic information into RNA molecules. The transcription cycle is divided into three key stages: initiation, elongation, and termination, each driven by specific molecular mechanisms.Initiation of TranscriptionIn bacteria, transcription begins when the RNA polymerase core enzyme associates with a sigma factor to form a holoenzyme. For example, the E. coli sigma factor called σ70 forms a holoenzyme, which recognizes the -10 (Pribnow box)...

